Rotor unit, rotating electrical machine, and method for manufacturing rotor unit

ABSTRACT

A rotor unit includes a rotor core made of laminated steel sheets that are vertically laminated, and a holder made of resin. The rotor core and the holder are fixed together through insert molding. For this reason, the process of manufacturing the rotor core and the holder is shortened. Additionally, in the outer peripheral surface of the rotor core, a portion of resin that defines the holder is present between the plurality of steel sheets that defines the rotor core. For this reason, the fixing strength of the rotor core and the holder improves. Additionally, since a separation between the rotor core and the holder is prevented, magnets can be easily press-fitted.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a rotor unit, a rotating electricalmachine, and a method for manufacturing a rotor unit.

2. Description of the Related Art

In the related art, an inner rotor type motor that rotates a rotor unithaving magnets inside a coil is known. For example, WO-A 2006-008964discloses a brushless motor including a stator, and a rotor arrangedinside the stator.

The rotor of WO-A 2006-008964 includes a rotor shaft, a rotor core, amagnet holder, and six rotor magnets. Paragraph 0026 of WO-A 2006-008964discloses that the rotor core is fixed to the rotor shaft, and the sixrotor magnets are attached to an outer periphery of the rotor core.Additionally, Paragraph 0027 of WO-A 2006-008964 discloses that themagnet holder is fixed to the rotor shaft.

RELATED ART DOCUMENT

-   [Patent Document 1] WO-A 2006-008964

Additionally, Paragraph 0029 of WO-A 2006-008964 descloses that afitting projection of the magnet holder is fitted into an electrodeholder attachment groove formed at an outer peripheral portion of therotor core. In WO-A 2006-008964, such fitting prevents a holder arm ofthe magnet holder from slipping out of the rotor core in a radialdirection.

However, WO-A 2006-008964 does not disclose how to obtain the axialfixing strength between the rotor core and the magnet holder.Particularly, if the rotor core and the magnet holder are not firmlyfixed in an axial direction when the magnets are press-fitted to themagnet holder in the axial direction, there is a concern that the rotorcore and the magnet holder may be separated from each other due to theload at the time of press-fitting.

An object of the invention is to provide the technique of improving thefixing strength between a rotor core and a holder in a rotor unit of arotating electrical machine.

SUMMARY OF THE INVENTION

A rotor unit for a rotating electrical machine that is a first exemplaryinvention of the present application includes an annular rotor core madeof laminated steel sheets that are vertically laminated; a plurality ofmagnets arranged in a circumferential direction around the rotor core;and a holder made of resin that holds the magnets. The holder has aplurality of partitioning portions that extends vertically along anouter peripheral surface of the rotor core, and a coupling portion thatconnects the plurality of partitioning portions. The rotor core and theholder are fixed by insert molding. In the outer peripheral surface ofthe rotor core, a portion of resin that constitutes the holder ispresent between the plurality of steel sheets that constitutes the rotorcore. The magnet is press-fitted into a pair of partitioning portionsthat is mutually adjacent.

A second exemplary invention of the present application is a method formanufacturing a rotor unit for a rotating electrical machine includingan annular rotor core made of laminated steel sheets that are verticallylaminated, a plurality of magnets arranged in a circumferentialdirection around the rotor core, and a holder made of resin that holdsthe magnets. The manufacturing method includes the following steps. Oneis a) arranging the rotor core inside a mold, injecting resin in afluidized state into the mold, and insert-molding the holder in a shapehaving a plurality of partitioning portions that extends verticallyalong an outer peripheral surface of the rotor core, and a couplingportion that connects the partitioning portions. Another is b)press-fitting the magnet to the pair of partitioning portions that aremutually adjacent after step a).

According to the first exemplary invention of the present application,in the outer peripheral surface of the rotor core, a portion of resinthat constitutes the holder is present between the plurality of steelsheets that constitutes the rotor core. This improves the fixingstrength of the rotor core and the holder.

According to the second exemplary invention of the present application,the manufacturing process of the rotor core and the holder is shortenedby the insert molding. Additionally, a portion of resin that constitutesthe holder is present between the plurality of steel sheets thatconstitutes the rotor core. This improves the fixing strength of therotor core and the holder. Additionally, since the separation betweenthe rotor core and the holder is suppressed, the magnets can be easilypress-fitted.

The present invention is arranged to achieve an improvement inperpendicularity of the upper end surface of the thrust portion withrespect to the outside surface of the shaft.

The above and other elements, features, steps, characteristics andadvantages of the present invention will become more apparent from thefollowing detailed description of the preferred embodiments of thepresent invention with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a rotor unit.

FIG. 2 is a longitudinal sectional view in the vicinity of a boundaryportion between a rotor core and a holder.

FIG. 3 is a longitudinal sectional view of a motor.

FIG. 4 is a perspective view of the rotor unit.

FIG. 5 is a top view of the rotor unit.

FIG. 6 is a longitudinal sectional view of the rotor unit.

FIG. 7 is a partially perspective view of the rotor core and a magnetholder.

FIG. 8 is a flowchart showing a manufacturing procedure of the rotorunit.

FIG. 9 is a longitudinal sectional view showing the state when insertmolding is performed.

FIG. 10 is a partially longitudinal cross-sectional view of the rotorunit before a magnet is press-fitted.

FIG. 11 is a partially longitudinal sectional view of the rotor unitafter the magnet is press-fitted.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Exemplary embodiments of the invention will be described below,referring to the drawings. In addition, the shapes and positionalrelationship of respective portions will be described with a directionalong the central axis of a rotating electrical machine being a verticaldirection. However, this merely defines the vertical direction for theconvenience of description, and does not limit the posture of a rotorunit and a rotating electrical machine related to the invention whenbeing used.

FIG. 1 is a perspective view of a rotor unit 32A for a rotatingelectrical machine related to one embodiment of the invention. As shownin FIG. 1, the rotor unit 32A includes a rotor core 41A, a holder 42A,and a plurality of magnets 43A.

The rotor core 41A is an annular member made of laminated steel sheetsthat are vertically laminated. The holder 42A is a member made of resin,which holds the magnets 43A. The holder 42A has a plurality ofpartitioning portions 60A and a coupling portion 70A. The plurality ofpartitioning portions 60A extends vertically along the outer peripheralsurface of the rotor core 41A, respectively. The coupling portion 70Aconnects the plurality of partitioning portions 60A. The plurality ofmagnets 43A is arranged in the circumferential direction around therotor core 41A. Each magnet 43A is press-fitted into a pair ofpartitioning portions 60 that is mutually adjacent.

When the rotor unit 32A is manufactured, first, the rotor core 41A isarranged inside a mold. Then, resin in a fluidized state is injectedinto the mold. By injecting resin, the holder 42A is insert-molded in ashape having the plurality of partitioning portions 60A and a couplingportion 70A. Thereafter, the magnet 43A is press-fitted between a pairof partitioning portions 60A that is mutually adjacent.

As such, in the present embodiment, the rotor core 41A and the holder42A are fixed by insert molding. For this reason, the process ofmanufacturing the rotor core 41A and the holder 42A is shortened. FIG. 2is a longitudinal sectional view in the vicinity of a boundary portionbetween the rotor core 41A and the holder 42A. As shown in FIG. 2, aportion of the resin that constitutes the holder 42A is present among aplurality of steel sheets 411A that constitutes the rotor core 41A inthe outer peripheral surface of the rotor core 41A. This firmly fixesthe rotor core 41A and the holder 42A. Additionally, since theseparation between the rotor core 41A and the holder 42A is suppressed,the magnets 43A can be easily press-fitted.

Subsequently, a more specific embodiment of the invention will bedescribed.

FIG. 3 is a longitudinal sectional view of the motor 1 that becomes anexample of a rotating electrical machine. The motor 1 of the presentembodiment is mounted on an automobile, and is used in order to generatea driving force for power steering. As shown in FIG. 3, the motor 1includes a stationary portion 2 and a rotating portion 3. The rotatingportion 3 is rotatably supported with respect to the stationary portion2.

The stationary portion 2 of the present embodiment has a housing 21, alid portion 22, an armature 23, a lower bearing 24, and an upper bearing25.

The housing 21 is a bottomed, substantially cylindrical housing thataccommodates the armature 23, the lower bearing 24, and the rotatingportion 3 therein. A recess 211 that holds the lower bearing 24 isformed at the center of the bottom of the housing 21. The lid portion 22is a plate-shaped member that closes an upper opening of the housing 21.A circular hole 221 that holds the upper bearing 25 is formed at thecenter of the lid portion 22.

The armature 23 generates magnetic flux according to a driving current.The armature 23 has a stator core 26 and a coil 27. The stator core 26is made of laminated steel sheets in which a plurality of steel sheetsis laminated in an axial direction (a direction along the central axis9; this is the same in the following). The stator core 26 has an annularcore back 261, and a plurality of teeth 262 that protrude toward theinside in a radial direction (a direction orthogonal to the central axis9; this is the same in the following) from the core back 261. The coreback 261 is fixed to the inner peripheral surface of the side wall ofthe housing 21. The coil 27 is constituted by conducting wires that arewound around each tooth 262 of the stator core 26.

The lower bearing 24 and the upper bearing 25 rotatably support a shaft31 on the side of the rotating portion 3. Ball bearings that allow anouter ring and an inner ring to rotate relatively via balls are used forthe lower bearing 24 and the upper bearing 25 of the present embodiment.

An outer ring 241 of the lower bearing 24 is fixed to the recess 211 ofthe housing 21. Additionally, an outer ring 251 of the upper bearing 25is fixed to the edge of the circular hole 221 of the lid portion 22. Onthe other hand, inner rings 242 and 252 of the lower bearing 24 and theupper bearing 25 are fixed to the shaft 31. For this reason, the shaft31 is rotatably supported with respect to the housing 21 and the lidportion 22.

The rotating portion 3 of the present embodiment has the shaft 31, apair of rotor units 32 and 33, and a cover 34.

The shaft 31 is a substantially cylindrical member that extends in thevertical direction along the central axis 9. The shaft 31 rotates aboutthe central axis 9, and is supported by the above-described lowerbearing 24 and upper bearing 25. Additionally, the shaft 31 has a head311 that protrudes upward from the lid portion 22. The head 311 iscoupled to a power steering device of an automobile via a powertransmission mechanism, such as a gear.

The pair of rotor units 32 and 33 and the cover 34 rotate along with theshaft 31 radially inside the armature 23. The pair of rotor units 32 and33 has a rotor core 41, a magnet holder 42, and a plurality of magnets43, respectively. The pair of rotor units 32 and 33 is arranged in theaxial direction in a state where the units are turned upside down. Thedetailed structure of the rotor units 32 and 33 will be described below.

The cover 34 is a substantially cylindrical member that holds the pairof rotor units 32 and 33. The cover 34 covers the outer peripheralsurface of the rotor units 32 and 33 and portions of upper and lower endsurfaces of the rotor units. Thereby, the pair of rotor units 32 and 33is maintained in a state where the units are brought close to each otheror brought into contact with each other.

In such a motor 1, if a driving current is applied to the coil 27 of thestationary portion 2, radial magnetic flux is generated in the pluralityof teeth 262 of the stator core 26. Then, circumferential torque isgenerated by the action of the magnetic flux between the teeth 262 andthe magnet 43, and the rotating portion 3 rotates about the central axis9 with respect to the stationary portion 2. If the rotating portion 3rotates, a driving force is transmitted to the power steering devicecoupled to the shaft 31.

As described above, the motor 1 of the present embodiment has the pairof rotor units 32 and 33. The detailed structure of the rotor unit 32arranged on the lower side will be described below. Although the rotorunit 33 arranged on the upper side is arranged in a state where therotor unit 32 arranged on the lower side is vertically reversed, sincethe structure itself thereof is equivalent to that of the lower rotorunit 32, duplicate description thereof will be omitted.

FIG. 4 is a perspective view of the rotor unit 32. FIG. 5 is a top viewof the rotor unit 32. As shown in FIGS. 4 and 5, the rotor unit 32 hasthe rotor core 41, the magnet holder 42, and the plurality of magnets43.

The rotor core 41 is an annular member fixed to the shaft 31. The rotorcore 41 is made of laminated steel sheets in which electromagnetic steelsheets are vertically laminated. The rotor core 41 of the presentembodiment has a regular polygonal columnar appearance. A through hole51 that allows the shaft 31 to be inserted therethrough is provided atthe center of the rotor core 41. Additionally, the outer peripheralsurface of the rotor core 41 is provided with a plurality of grooveportions 52 that extends in the axial direction. The groove portions 52are depressed radially inward at boundary portions of a plurality ofplanes that constitutes the outer peripheral surface of the rotor core41.

The magnet holder 42 is a member that holds the magnets 43 made ofresin. The magnet holder 42 has a plurality of partitioning portions 60,and a coupling portion 70 that connects lower ends of the plurality ofpartitioning portions 60. The plurality of partitioning portions 60 isarranged at equal intervals in the circumferential direction. Eachpartitioning portion 60 extends in the axial direction along the lateralface of the rotor core 41 in the vicinity of each groove portion 52 ofthe rotor core 41. The coupling portion 70 is a circular portion locatedbelow the plurality of partitioning portions 60. A radial inside portionof the coupling portion 70 comes in contact with the lower surface ofthe rotor core 41.

FIG. 6 is a longitudinal sectional view of the rotor unit 32 seen fromthe position A-A in FIG. 5. In the present embodiment, the magnet holder42 is formed on the surface of the rotor core 41 by insert molding. Wheninsert molding is performed, resin is injected into a mold for moldingin a state where the rotor core 41 is arranged in advance inside themold. Then, the rotor core 41 and the magnet holder 42 are fixed to eachother with hardening of the resin.

In FIG. 6, a portion of a boundary between the rotor core 41 and themagnet holder 42 is shown in an enlarged manner. As shown in theenlarged view, gaps 412 are present between the plurality of steelsheets 411 that constitutes the rotor core 41 in the vicinity of theouter peripheral surface of the rotor core 41. A portion of the resinthat constitutes the magnet holder 42 is present in the gaps 412. Thisis formed as resin in a fluidized state enters the gaps 412 of the rotorcore 41 when insert molding is performed.

As for the rotor core 41 and the magnet holder 42 of the presentembodiment, both the members slightly bite into each other at theboundary portion thereof. Thereby, the rotor core 41 and the magnetholder 42 are firmly fixed. Particularly, resin is present in an axialgap formed between a steel sheet 411 and a steel sheet 411. For thisreason, the axial relative movement between the rotor core 41 and themagnet holder 42 is suppressed.

The plurality of steel sheets 411 that constitutes the rotor core 41 isobtained by punching, respectively. For this reason, as shown in theenlarged view in FIG. 6, a curved portion 413 according to the directionof punching is formed at the end of each steel sheet. In the presentembodiment, the curved portion 413 is curved toward the upside. For thisreason, upward coming-off of the rotor core 41 with respect to themagnet holder 42 is further suppressed.

Additionally, as shown in FIGS. 4 and 5, each partitioning portion 60 ofthe present embodiment has an engaging portion 61 that is held in eachgroove portion 52 of the rotor core 41. At the time of insert molding,the engaging portion 61 is formed as the resin that has flowed into thegroove portion 52 hardens. For this reason, a gap is not easilygenerated between the engaging portion and the rotor core 41 in thegroove portion 52. Accordingly, the rotor core 41 and the magnet holder42 are more firmly fixed.

Particularly, in the present embodiment, the engaging portion 61 ofwhich the dimension in a width direction increases toward the inside inthe radial direction engages the groove portion 52 of which thedimension in the width direction decreases toward the outside in theradial direction. This further suppresses the radial separation of therotor core 41 and the magnet holder 42.

The plurality of magnets 43 is arranged around the rotor core 41. Eachmagnet 43A is substantially arcuate on the external diameter sidethereof and substantially linear on the internal diameter side thereof,and is press-fitted into a pair of partitioning portions 60 that ismutually adjacent. The radial outside surface of the magnet 43 is amagnetic polar surface that faces the armature 23. The plurality ofmagnets 43 is arranged at equal intervals so that an N magnetic polarsurface and an S magnetic polar surface are alternately arranged in thecircumferential direction. In addition, for example, an Nd—Fe—B alloybased sintered magnet can be used for a magnet 43.

FIG. 7 is a partial perspective view of the rotor core 41 and the magnetholder 42. The detailed shape of the magnet holder 42 will be described,referring to FIGS. 4, 5, and 7.

The partitioning portion 60 of the magnet holder 42 has the columnarportion 62 and a wall portion 63. The columnar portion 62 is a portionthat extends in the axial direction between the magnets 43 that aremutually adjacent. The wall portion 63 is a portion that spreads towardone side or the other side in the circumferential direction from thecolumnar portion 62. The radial outside surface of the magnet 43 ispartially covered with the wall portion 63.

An upper end of the wall portion 63 is located lower than an upper endof the rotor core 41. For this reason, when a magnet 43 is attached, thelower end of the magnet 43 is brought into contact with the lateral faceof the rotor core 41, so that the magnet 43 can be positioned in theradial direction. The magnet 43 positioned in the radial direction canbe press-fitted radially inward of the wall portion 63.

Additionally, the upper end of the wall portion 63 is located lower thanan upper end of the columnar portion 62. For this reason, when a magnet43 is attached, the lower end of the magnet 43 can be easily insertedbetween the pair of columnar portions 62 that is mutually adjacent.Additionally, the magnet 43 can be positioned in the radial direction bythe pair of columnar portions 62, and then, the magnet 43 can then bepress-fitted radially inward of the wall portion 63.

If the magnet 43 is positioned in the radial direction and thecircumferential direction in this way, the bias of the load at the timeof press-fitting can be suppressed. Accordingly, it is possible tosuppress the magnet 43 from shaving off the partitioning portions 60 ofthe magnet holder 42 and generating dust at the time of press-fitting.

Additionally, in the present embodiment, an inclined surface 631 isprovided in the vicinity of an upper end of the radial inside surface ofthe wall portion 63. The inclined surface 631 gradually approaches theouter peripheral surface of the rotor core 41 downward from an upperend. The inclined surface 631 guides the magnet 43 radially inward ofthe wall portion 63 at the time of the press-fitting of the magnet 43.This facilitates the press-fitting work of the magnet 43. Additionally,as the magnet 43 is guided to a proper position, the bias of the load atthe time of press-fitting is further suppressed. As a result, generationof dust accompanying the press-fitting is further suppressed.

Additionally, if such an inclined surface 631 is provided, the vicinityof the upper end of the wall portion 63 can be easily separated from amold at the time of insert molding. In this way, the inclined surface631 has technical value at the time of both press-fitting and insertmolding.

The coupling portion 70 has a bottom 71 located below the magnet 43.That is, the bottom 71 is also arranged at a circumferential positionbetween the partitioning portions 60 that are mutually adjacent. Thelower surface of the magnet 43 after press-fitting faces the uppersurface of the bottom 71 in the axial direction, and the lower surfaceof the magnet 43 and the upper surface of the bottom 71 separate from orcome into contact with each other. Additionally, the bottom 71 has arecess 72 below both ends the magnet 43 in the circumferentialdirection. The recess 72 of the present embodiment is provided at aposition surrounded by the lateral face of the rotor core 41, thecolumnar portion 62, and the wall portion 63.

Even if the magnet 43 contacts the columnar portion 62 or the wallportion 63 to generate dust at the time of the press-fitting of themagnet 43, the dust is received in the recess 72. For this reason, it ispossible to suppress a problem of the dust being caught between theupper surface of the bottom 71 and the lower surface of the magnet 43,whereby the axial position of the magnet 43 deviates. Additionally, therecess 72 is sealed by the lower surface of the magnet 43 afterpress-fitting, and becomes a closed space. For this reason, scatteringof the dust received in the recess 72 to the outside is prevented.

In addition, at the time of the press-fitting of the magnet 43, thecolumnar portion 62 receives a stronger load from the magnet 43 than thewall portion 63. Accordingly, the columnar portion 62 becomes a sourceof dust more easily than the wall portion 63. If this point is takeninto consideration, it is preferable that the recess 72 be provided atleast at a position adjacent to the lower end of the columnar portion62.

Subsequently, an example of a method for manufacturing the rotor unit 32will be described, referring to FIGS. 8 to 11. FIG. 8 is a flowchartshowing a manufacturing procedure of the rotor unit 32. FIG. 9 is alongitudinal sectional view showing the state where insert molding isperformed. The position of the section of FIG. 9 is equivalent to theposition A-A in FIG. 5 after manufacture. Additionally, FIGS. 10 and 11are longitudinal sectional views showing the state when the magnet 43 ispress-fitted to the magnet holder 42. The positions of the sections ofFIGS. 10 and 11 are equivalent to the position B-B in FIG. 5 aftermanufacture.

When the rotor unit 32 is manufactured, first, a pair of molds 81 and 82and the rotor core 41 made in advance are prepared (Step S1). The pairof molds 81 and 82 form a cavity 83 inside the pair of molds 81 and 82by bringing mutually opposed surfaces into contact with each other. Thecavity 83 corresponds to the shape of the rotor core 41 and the magnetholder 42. The rotor core 41 is made of laminated steel sheets in whichsteel sheets subjected to punching are laminated in the axial direction.

Next, the rotor core 41 is arranged inside the pair of molds 81 and 82(Step S2). Here, first, the rotor core 41 is set inside one mold 81.Then, the upper portion of the mold 81 is closed by the other mold 82.Thereby, the cavity 83 is formed inside molds 81 and 82, bringing astate where the rotor core 41 is arranged in the cavity 83.

Thereafter, resin 421 in a fluidized state is injected into the cavity83 (Step S3). Here, as shown in FIG. 9, the resin 421 in the fluidizedstate is injected into the cavity 83 through a runner 821 provided inthe mold 82. The resin 421 in the fluidized state also flows into thegroove portions of the rotor core 41. Additionally, in the lateral faceof the rotor core 41, the resin 421 in a fluidized state also entersgaps among the plurality of steel sheets 411 that constitute the rotorcore 41.

If the resin 421 in the fluidized state spreads in the cavity 83, theresin 421 in the mold 81 and 82 is cooled and solidified (Step S4). Theresin 421 in the mold 81 and 82 is solidified into the magnet holder 42.The magnet holder 42 is molded in a shape having the plurality ofpartitioning portions 60 and the coupling portion 70, including theabove engaging portion 61, the columnar portion 62, the wall portion 63,the inclined surface 631, the bottom 71, and the recess 72.

Additionally, the rotor core 41 and the magnet holder 42 are fixed alongwith the solidification of the resin. Thereby, in the lateral face ofthe rotor core 41, a portion of the resin that constitutes the magnetholder 42 is present among the plurality of steel sheets 411 thatconstitutes the rotor core 41. Thereby, the rotor core 41 and the magnetholder 42 are firmly fixed.

Thereafter, the pair of molds 81 and 82 are opened, and the rotor core41 and the magnet holder 42 are separated from the molds 81 and 82 (StepS5). The inclined surface 631 is formed at the upper end of the wallportion 63 of the magnet holder 42. For this reason, the wall portion 63can be easily separated from the mold 82.

The above Steps S1 to S5 are the procedure that becomes an example ofthe insert molding. Thereby, the rotor core 41 and the magnet holder 42of FIG. 6 are obtained. At the time of insert molding, both the moldingof the magnet holder 42 and the fixation of the rotor core and themagnet holder 42 are performed. For this reason, the process ofmanufacturing the rotor core 41 and the magnet holder 42 is shortened.

Subsequently, a magnet 43 is prepared, and the magnet 43 is positionedat a position to be inserted with respect to the rotor core 41 and themagnet holder 42 (Step S6). Here, first, a lower end of the magnet 43 isbrought close to the lateral face of the rotor core 41 above the wallportion 63 as indicated by an arrow 84 in FIG. 10. Then, the lower endof the magnet 43 is brought into contact with the lateral face of therotor core 41. This determines the radial position of the magnet 43.Further, the lower end of the magnet 43 is inserted between a pair ofcolumnar portions 62 that is mutually adjacent. This determines thecircumferential position of the magnet 43.

Next, the magnet 43 is moved downward as indicated by an arrow 85 inFIG. 10. Here, the inclined surface 631 is provided at the upper end ofthe wall portion 63. For this reason, even if the position of the magnet43 has deviated slightly, if the lower end of the magnet 43 is movedalong the inclined surface 631, the magnet 43 is guided radially inwardof the wall portion 63. This more precisely determines the position ofthe magnet 43.

Thereafter, the magnet 43 is press-fitted to the pair of columnarportions 62 that is mutually adjacent and the wall portion 63 (Step S7).In the above step S6, the magnet 43 is positioned in the radialdirection and in the circumferential direction. For this reason, thebias of load at the time of press-fitting is suppressed. As a result,generation of dust accompanying the press-fitting is suppressed.

Additionally, the magnet holder 42 of the present embodiment has therecess 72 below both ends the magnet 43 in the circumferentialdirection. For this reason, even if the magnet 43 shaves off thepartitioning portion 60 generating dust 86 at the time of press-fitting,as shown in FIG. 11, the dust 86 can be received in the recess 72. Forthis reason, it is possible to suppress a problem of the dust beingcaught between the upper surface of the bottom 71 and the lower surfaceof the magnet 43, whereby the axial position of the magnet 43 deviates.Additionally, the recess 72 is sealed by the lower surface of the magnet43 after press-fitting. For this reason, scattering the dust 86 receivedin the recess 72 to the outside is prevented.

Additionally, the rotor core 41 and the magnet holder 42 are firmlyfixed by insert molding. For this reason, the load at the time of thepress-fitting of the magnet 43 suppresses the rotor core 41 and themagnet 42 from being separated from each other. Accordingly, the magnet43 can be easily press-fitted.

If a plurality of magnets is intended to be arranged inside the mold atthe time of the above insert molding, it is necessary to fix the magnetsto the surface of the rotor core by adhesion or the like. In contrast,in the present embodiment, the magnet 43 is press-fitted into the magnetholder 42 after insert molding is completed and hardening is made. Forthis reason, the time and effort to adhere the magnet 43 to the rotorcore 41 can be saved. Additionally, a plurality of magnets 43 can beeasily positioned with high precision.

Features of the above-described preferred embodiments and themodifications thereof may be combined appropriately as long as noconflict arises.

While preferred embodiments of the present invention have been describedabove, it is to be understood that variations and modifications will beapparent to those skilled in the art without departing from the scopeand spirit of the present invention. The scope of the present invention,therefore, is to be determined solely by the following claims.

The inclined surface 631 of the magnet holder 42 may be a curved surfaceas shown in FIG. 7, or may be a planar surface. Additionally, achamfered inclined surface may be provided not only at the magnet holder42 but also at the lower end of the magnet 43. If so, the magnet 43 canbe more smoothly press-fitted to the magnet holder 42. Additionally,generation of dust accompanying the press-fitting can be furthersuppressed.

The number of the partitioning portions 60 of the magnet holder 42 andthe number of the magnets 43 may be different numbers from those of theabove embodiment. Additionally the coupling portion 70 of the magnetholder 42 may connect portions other than the lower ends of theplurality of partitioning portions 60.

Additionally, the number of the rotor units 32 included in the rotatingportion 3 of the motor 1 may be one, or may be three or more.

Additionally, the rotating electrical machine of the invention may bethe above motor 1 for power steering, or may be motors used for otherportions of an automobile. For example, the rotating electrical machineof the invention may be a motor for generating the driving force of anelectric motorcar. Additionally, the rotating electrical machine of theinvention may be a motor used for an electric power-assisted bicycle, anelectric motorcycle, home electronics, OA equipment, a medicalinstrument, or the like.

Additionally, a generator can also be configured with the structureequivalent to the motor of the above embodiment or modification. Therotating electrical machine of the invention may be a generator used foran automobile, an electric power-assisted bicycle, wind powergeneration, or the like.

Additionally, the respective elements appeared in the above embodimentor modification may be appropriately combined together within a rangewhere inconsistency does not occur.

The invention can be used for a rotor unit, a rotating electricalmachine, and a method for manufacturing a rotor unit.

DESCRIPTION OF REFERENCE NUMERALS AND SIGNS

-   -   1: motor    -   2: stationary portion    -   3: rotating portion    -   9: central axis    -   21: housing    -   22: lid portion    -   23: armature    -   24: lower bearing    -   25: upper bearing    -   26: stator core    -   27: coil    -   31: shaft    -   32, 32A, 33: rotor unit    -   34: cover    -   41, 41A: rotor core    -   42: magnet holder    -   42A: holder    -   43, 43A: magnet    -   51: through hole    -   52: groove portion    -   60, 60A: partitioning portion    -   61: engaging portion    -   62: columnar portion    -   63: wall portion    -   70, 70A: coupling portion    -   71: bottom    -   72: recess    -   81, 82: mold    -   411, 411A: steel sheet    -   412: gap    -   413: curved portion    -   421: resin in fluidized state    -   631: inclined surface

1-13. (canceled)
 14. A rotor unit for a rotating electrical machinecomprising: an annular rotor core including laminated steel sheets thatare vertically laminated; a plurality of magnets arranged in acircumferential direction around the rotor core; and a holder made ofresin that is arranged to hold the plurality of magnets; wherein theholder includes a plurality of partitioning portions that extendsvertically along an outer peripheral surface of the rotor core, and acoupling portion that connects the plurality of partitioning portions;the rotor core and the holder are made of insert molded material so asto be fixed together; a portion of resin that defines the holder ispresent between the plurality of steel sheets that defines the rotorcore in the outer peripheral surface of the rotor core; and one of theplurality of magnets is press-fitted into a pair of the plurality ofpartitioning portions that are mutually adjacent.
 15. The rotor unitaccording to claim 14, wherein the partitioning portion includes: acolumnar portion located between a pair of the plurality of magnets thatare mutually adjacent; and a wall portion that partially covers a radialoutside surface of the pair of the plurality of magnets; and an innerperipheral surface of the wall portion includes an inclined surface thatgradually approaches the outer peripheral surface of the rotor coredownward from an upper end.
 16. The rotor unit according to claim 15,wherein an upper end of the wall portion is located lower than an upperend of the rotor core.
 17. The rotor unit according to claim 15, whereinan upper end of the wall portion is located lower than an upper end ofthe columnar portion.
 18. The rotor unit according to claim 14, whereinthe coupling portion includes a bottom that faces a lower surface of theone of the plurality of magnets; the bottom includes a recess locatedbelow two ends of the one of the plurality of magnets in thecircumferential direction; and the recess is sealed by the one of theplurality of magnets.
 19. The rotor unit according to claim 14, whereinthe rotor core includes a plurality of vertically extending grooveportions in an outer peripheral surface thereof; the plurality of grooveportions have a shape of which a dimension in a width directiondecreases toward an outside in a radial direction; and the plurality ofpartitioning portions include engaging portions held within theplurality of groove portions.
 20. The rotor unit according to claim 14,wherein ends of the plurality of steel sheets are curved toward anupside in a vicinity of the outer peripheral surface of the rotor core.21. A rotating electrical machine comprising: a stationary portion; anda rotating portion rotatably supported with respect to the stationaryportion; wherein the rotating portion includes the rotor unit accordingto claim 14, and a shaft inserted into the rotor core; and thestationary portion includes a bearing that rotatably supports the shaft,and an armature arranged radially outside the rotor unit.
 22. A methodof manufacturing a rotor unit for a rotating electrical machineincluding an annular rotor core including laminated steel sheets thatare vertically laminated, a plurality of magnets arranged in acircumferential direction around the rotor core, and a holder made ofresin that holds the plurality of magnets, the method comprising: a)arranging the rotor core inside a mold, and injecting resin in a fluidstate into the mold to insert-mold the holder, wherein a plurality ofpartitioning portions that extends vertically along an outer peripheralsurface of the rotor core, and a coupling portion that connects thepartitioning portions are formed by insert molding; and b) a magnet ofthe plurality of magnets is press-fitted to a pair of the plurality ofpartitioning portions that are mutually adjacent after step a).
 23. Themanufacturing method according to claim 22, wherein in step a), theplurality of partitioning portions is molded in a shape including acolumnar portion located between ones of the plurality of magnets thatare mutually adjacent, and a wall portion that partially covers radialoutside surfaces of the ones of the plurality of magnets that aremutually adjacent; and an inclined surface that gradually approaches theouter peripheral surface of the rotor core downward from an upper end ismolded on an inner peripheral surface of the wall portion.
 24. Themanufacturing method according to claim 23, wherein an upper end of thewall portion is molded at a position lower than an upper end of therotor core in step a).
 25. The manufacturing method according to claim23, wherein an upper end of the wall portion is molded at a positionlower than an upper end of the columnar portion in step a).
 26. Themanufacturing method according to claim 22, wherein the coupling portionis molded in a shape including a bottom arranged at a circumferentialposition between the partitioning portions that are mutually adjacent,and a recess located at both ends of the bottom in a circumferentialdirection, in step a); and the magnet of the plurality of magnets sealsthe recess in step b).